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Winthrop University Digital Commons @ Winthrop University Graduate eses e Graduate School 5-2019 A Test of the Use of Timber Wolf (Canis lupus) Urine to Reduce Coyote (Canis latrans) Depredation Rates on Loggerhead Sea Turle (Carea carea) Nests Michael Wauson Winthrop University, [email protected] Follow this and additional works at: hps://digitalcommons.winthrop.edu/graduatetheses Part of the Behavior and Ethology Commons , Biology Commons , and the Terrestrial and Aquatic Ecology Commons is esis is brought to you for free and open access by the e Graduate School at Digital Commons @ Winthrop University. It has been accepted for inclusion in Graduate eses by an authorized administrator of Digital Commons @ Winthrop University. For more information, please contact [email protected]. Recommended Citation Wauson, Michael, "A Test of the Use of Timber Wolf (Canis lupus) Urine to Reduce Coyote (Canis latrans) Depredation Rates on Loggerhead Sea Turle (Carea carea) Nests" (2019). Graduate eses. 108. hps://digitalcommons.winthrop.edu/graduatetheses/108

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Page 1: A Test of the Use of Timber Wolf (Canis lupus) Urine to Reduce … WolfUrinetoreduceCo.… · I used dispensers filled with wolf urine to simulate timber wolf (Canis lupus) activity

Winthrop UniversityDigital Commons @ Winthrop

University

Graduate Theses The Graduate School

5-2019

A Test of the Use of Timber Wolf (Canis lupus)Urine to Reduce Coyote (Canis latrans)Depredation Rates on Loggerhead Sea Turle(Caretta caretta) NestsMichael WausonWinthrop University, [email protected]

Follow this and additional works at: https://digitalcommons.winthrop.edu/graduatethesesPart of the Behavior and Ethology Commons, Biology Commons, and the Terrestrial and

Aquatic Ecology Commons

This Thesis is brought to you for free and open access by the The Graduate School at Digital Commons @ Winthrop University. It has been accepted forinclusion in Graduate Theses by an authorized administrator of Digital Commons @ Winthrop University. For more information, please [email protected].

Recommended CitationWauson, Michael, "A Test of the Use of Timber Wolf (Canis lupus) Urine to Reduce Coyote (Canis latrans) Depredation Rates onLoggerhead Sea Turle (Caretta caretta) Nests" (2019). Graduate Theses. 108.https://digitalcommons.winthrop.edu/graduatetheses/108

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A TEST OF THE USE OF TIMBER WOLF (CANIS LUPUS) URINE TO REDUCE

COYOTE (CANIS LATRANS) DEPREDATION RATES ON LOGGERHEAD SEA

TURTLE (CARETTA CARETTA) NESTS

A Thesis

Presented to the Faculty

of the College of Arts and Sciences

in partial Fulfillment

of the

Requirements for the Degree

of

Master of Science

In Biology

Winthrop University

May, 2019

By

Michael Wauson

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Abstract

Loggerhead sea turtles are currently listed as vulnerable by the International

Union of Conservation of Nature (IUCN) with a decreasing population trend. Over the

past four years, coyotes (Canis latrans) have depredated 24.18% of loggerhead sea turtle

(Caretta caretta) nests on the night they were laid on South Island beach at the Tom

Yawkey Wildlife Center, near Georgetown, SC. This has resulted in an estimated 4,002

eggs lost each year there. Over that time, a South Carolina Department of Natural

Resources (SCDNR) Turtle Technician Team patrolled the beach at dawn every morning

to cage and catalog loggerhead eggs and nests but were unable to cost-effectively protect

the nests the night the eggs are laid. To test a new method to dissuade coyote depredation,

I used dispensers filled with wolf urine to simulate timber wolf (Canis lupus) activity on

seven sections of the beach and left seven sections untreated as controls. There was an

apparent depression in depredation rates where urine was present compared to that of the

control areas. The results suggest this may be an example of exploitative competition in

the absence of interference competition. Furthermore, there may be kairomones in the

wolf urine that allow the exploitative competition to exist even when coyotes haven’t

been exposed to wolves in many generations. With daily teams patrolling the beaches

already, the use of wolf urine as a deterrent could be an inexpensive, non-invasive way of

reducing coyote depredation on loggerhead nests elsewhere.

With access to the DNR’s large data set I was able to test if there were any

naturally occurring potential influences that affected loggerhead nesting or coyote

depredation behavior. I was able to determine that nocturnal atmospheric conditions,

mean daily temperature, nocturnal precipitation, nocturnal wind conditions, moon phase

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grouping and nocturnal tide types had no effect on or correlation with loggerhead nesting

or coyote depredation behavior.

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Acknowledgements

First and foremost, I would like to thank my thesis adviser, Bill Rogers, for

his tireless support, patience, and encouragement. Bill has helped me grow

as a person and a researcher over the last three years. Without his support, I

doubt I would have been able to complete a research project such as this. A

further thanks for his assistance in the field implementing my experiment.

I would also like to thank the other two members of my thesis committee,

Janice Chism and Jennifer Schafer, for guiding me in the construction and

writing of my thesis as well as answering my never-ending questions.

I want to give a huge thanks to the Tom Yawkey Wildlife Center for

allowing me to perform my experiment on their land and for the

transportation and housing while on the islands. A special thanks to Jamie

Dozier, Project Leader at the Tom Yawkey Wildlife Center, and the SCDNR

turtle technician team that collected all the data and kept an eye on the area

though-out the season.

Finally, I would like to thank my fellow graduate students for the constant

support and help throughout the year and my undergraduate assistant,

Stephanie Martin, for whom I would have never been able to get the project

off the ground without her tireless assistance.

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Table of Contents

I. Abstract i

II. Acknowledgments iii

III. List of Figures and Tables v

IV. Introduction 1

Natural History of Loggerhead Sea Turtles 2

Nesting Behavior 5

Conservation Issues 9

Natural History of Coyotes 13

History of Tom Yawkey Wildlife Center 16

History of Loggerheads on South Island 17

History of Loggerheads and Coyotes at Yawkey 18

Present Project 19

V. Materials and Methods

Layout and Execution 21

Statistical Analysis 24

VI. Results

Wolf Urine Effectiveness 25

Variables That May Affect Loggerhead Sea Turtle Behavior 27

Variables That May Affect Coyote Depredation Behavior 28

VII. Discussion

Wolf Urine as a Deterrent 28

Loggerhead Sea Turtle Nests Analysis 34

Coyote Depredation of Loggerhead Nest Analysis 35

Final Recommendations 35

VIII. Literature Cited 37

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List of Figures and Tables

IV. Introduction

Figure 1: Loggerhead Life Cycle 3

Figure 2: Nesting Loggerhead Tracks 7

Figure 3: Loggerhead Nesting Image 8

Figure 4: Tom Yawkey Wildlife Center Islands 17

VI. Results

Table 1: 30-Day Total Control Test 25

Table 2: 30-Day Urine Test 26

Table 3: 9-Day Total Control Test 26

Table 4: 9-Day Urine Test 27

Table 5: 2018 Comparison to 2015-2017 Data 27

VII. Discussion

Table 6: 2018 Nest Proportion Totals 29

Table 7: Extrapolated Nest Urine Data 29

IX. Appendix 1

Urine Dispenser Layout Diagram 44

X. Appendix 2

2015 South Island Loggerhead Nesting Data 45

2016 South Island Loggerhead Nesting Data 46

2017 South Island Loggerhead Nesting Data 47

2018 South Island Loggerhead Nesting Data W/ Treatment Zones 48

2018 South Island Depredation Data W/ Treatment Zones 49

2018 9-Day Nesting Data W/ Treatment Zones 50

2018 9-Day Depredation Data W/ Treatment Zones 51

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Introduction

Loggerhead sea turtles (Caretta caretta) are found throughout the subtropical and

temperate regions of the Mediterranean Sea and Pacific, Indian and Atlantic Oceans

(IUCN 2017A). This global distribution has made them the flagship species for sea turtle

conservation. In South Carolina alone, there are more than 1,100 participants, most of

them volunteers, working to secure a future for these majestic animals (SCDNR 2013).

The infatuation with sea turtles goes beyond just conservation work and can be seen in

merchandise such as t-shirts and jewelry as well as in the children’s movies A Turtle’s

Tale and Finding Nemo. Even with the public awareness about the need to protect

loggerheads and other sea turtles, populations are in decline, necessitating continued

conservation work.

Conservation efforts focused on protecting loggerhead sea turtle nests have had an

extensive history since they were listed as threatened throughout their range under the

Endangered Species Act of 1973 (National Marine Fisheries Service (NMFS) 2008).

However, most of those conservation methods do not protect the nests the night the eggs

are laid, a point at which the eggs are particularly susceptible to predators such as

coyotes, raccoons (Procyon lotor), boars (Sus scrofa), and ghost crabs (Ocypode

quadrata) (Engeman et al. 2006). To prevent this depredation, a technique is required to

be implemented to deter depredation 24/7 but have no effect on the turtles nesting.

The objective of this project was to tested a method to mitigate depredation by

coyotes, which is presently the most significant natural threat to loggerhead turtle nests

on South Island beach at the Tom Yawkey Wildlife Center near Georgetown, South

Carolina. Coyotes account for 85 to 90 percent of lost eggs every year on South Island

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beach (South Carolina Department of Natural Resources (SCDNR) 2017). All such losses

occur the night the eggs are laid (Pers. Obs). A technique that reduces the depredation of

nests by coyotes could potentially allow thousands more eggs to hatch. Therefore, I tested

an affordable method to protect sea turtle nests the night they are laid, which has the

potential to be used in the conservation of loggerhead and other sea turtle species.

Natural History of Loggerhead Sea Turtles

Lifecycle Stages

The loggerhead sea turtle’s lifecycle can be broken down into six stages: 1) eggs, 2)

hatchlings, 3) post-hatchlings, 4) oceanic juveniles, 5) neritic juveniles, and 6) adults

(NMFS 2008) (Figure 1). The nesting season runs from late April through early

September, with hatching occurring between late June and early November (NMFS

2008). Once the eggs are laid, they take on average 55-60 days to hatch (SCDNR Marine

Turtle Conservation Program 2013), with the pivotal temperature in the nest, defined as

the temperature that produces an equal number of males and females, being 29ᵒC (NMFS

2008).

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Figure 1. A simplified general locational life cycle of Atlantic Loggerheads (modified from Bolten 2003).

Loggerhead hatchlings require four to seven days to emerge from the sand after

hatching (Koen et al. 1994). Hatchlings usually emerge en masse at night. It is

hypothesized that they time emergence with the lowering of the sand temperature below a

certain point, which usually occurs after sunset (Moran et al. 1999). Once hatchlings

emerge from the sand, they head straight for the ocean, using the slope of the beach and

the reflection of light from the stars and the moon off the ocean surface, compared to

dark dunes, as a guide (Parker 1922). Many beachfront communities that have sea turtle

nests on their shores require beachside lights-out curfews during the hatching season to

ensure hatchlings do not become confused by artificial lighting (U.S. Fish and Wildlife

Service 1978). It has been shown that nesting females will nest in front of tall dark

objects on urban beaches to mitigate the effects of artificial light (Salmon et al. 1995).

Terrestrial Zone

•Nesting Beach (egg, hatchling life stages)

Neritic Zone

•Hatchling swim Frenzy (Post-Hatchling life stage) 20-30 hrs

Oceanic Zone

•Oceanic Juvenile life stage till about 7-11.5 years of age

Neritic Zone

•Neritic Juvenile Life Stage till carapace length reaches 90 cm

•Adult Life stage

Neritic and Oceanic Zones

•Reproductive ativities

•migration corridors for breeding habitats

Neritic Zone

• Philopatric reproductive process (returning to beach where female hatched)

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Once in the water, the 4 cm long hatchlings (measured as the length of the carapace)

begin a 20 to 30-hour swimming frenzy (post-hatchling life stage) that takes them away

from the coast into the open ocean, coming to rest in Sargassum spp., dead terrestrial

vegetation and/or debris in pelagic drift lines formed in current convergences (Carr 1986,

NMFS and FWS 1991, NOAA Fisheries 2017). This starts the oceanic juvenile stage.

The juveniles continue to ride the current convergences for the next 7 to 11.5 years,

growing to between 46 and 64 cm in carapace length (NMFS and FWS 1991). During

this life stage, juveniles increase in length approximately 2.9 to 5.4 cm a year on average

(Snover 2002). Juveniles consume a variety of organisms including cnidarians, salps,

pelagic snails, jellyfish, barnacles and crabs (Bjorndal 1997). Hatchling survival

probability to their second year is still unknown but is thought to be relatively low

(NMFS and FWS 1991). This part of the juvenile stage is often referred to as the lost

years due to the inability to track the hatchlings and young juveniles in the open ocean

until 2014. In 2014 Mansfield et al. showed that the juveniles rarely travel in continental

shelf waters, frequently leave currents associated with the North Atlantic Subtropical

Gyre, select surface water habitats that most likely provide a thermal benefit or refuge

which supports growth, foraging and survival. Their annual survival probability between

the ages of 2 and 6 is 91.1 percent (NMFS and FWS 1991).

The neritic zone is defined as nearshore and estuarine waters, with depths less than

200 meters, along continental margins and shelves. During the neritic juvenile life stage,

the turtles main prey items include jellyfish, mollusks, crabs, sea pens and fish bycatch

from shrimp trawlers (Burke et al. 1993, Plotkin et al. 1993, Seney 2003). The carapace

length of loggerheads in this phase ranges from 46 to 87 cm, with a growth rate of 1.8 to

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2.1 cm/year (Bjorndal et al. 2001). Individuals stay in this stage between 14 and 24 years,

depending on their size when they entered it. During the neritic juvenile stage, the annual

survivorship estimates drop to 64.3 Percent (Bjorndal et al. 2003).

Loggerheads are sexually mature when their carapace length reaches 90 cm, which

usually occurs between the ages of 17 and 33 years (MarineBio 2013, Drakes 2012). As

adults, loggerheads are considered the largest hard-shelled turtles, weighing around 114

kg (NMFS 2008). Adults can move between the oceanic and neritic zones and feed

mostly on Janthina spp. (small to medium-sized pelagic or planktonic sea snails), Velella

velella (pelagic hydrozoans), Lepas spp. (gooseneck barnacles), Planes spp. (crabs), and

Pyrosoma spp. (free-floating colonial tunicates) (Seney and Musick 2007, Parker et al.

2005).

As a result of nesting on land, there is a knowledge gap between male and female

life history’s. Females are easily tagged when nesting on the beach, and that data shows

that adult females spend as much as 25 years in the neritic zone (Dahlen et al. 2000).

Females are estimated to be reproductively viable for 25 years, but that may be an

underestimate due to tag loss and incomplete surveys (NMFS 2008). There is little data

on the movement and lifespan of adult male loggerheads because of the difficulty in

locating and tagging them (Loggerhead Marinelife Center 2017). The annual survival

probability of an adult loggerhead is estimated at 85 percent (Heppell et al. 2003).

Nesting Behavior

When females nest, they come up on the beach at night and lay between 100 and

126 eggs above the high tide line. As they move, the females leave clear carapace and

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elbow joint marks in the sand (Figure 2). Once a nesting site has been chosen, the

females turn around to face the ocean and begin to dig their nests. To excavate the egg

chamber, the females use their hind flippers to dig a flask-like chamber around 60 cm in

depth and 23-26 cm in width (Carthy et al. in Miller et al. 2003) (Figure 3). The actual

nest size correlates with several measurements of the nesting female such as carapace

length, width, and reproductive output (Carthy et al. in Miller et al. 2003). When

selecting a nesting site, females must balance between nesting too close to the ocean,

which could lead to inundation of the nest, and too far inland, which brings increased

threats of nest depredation, hatchling misorientation and predation of the female (Wood

and Bjorndal 2000). What determines the exact nest location is still poorly known. It is

believed that a nest site is chosen when several threshold cues possibly slope, salinity and

temperature among other environmental factors are reached (Wood and Bjorndal 2000).

Reproductive females will usually return to the same beach to nest every two to three

years, but the interval ranges from one to seven years (U.S. Fish and Wildlife Service

2018).

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Figure 2. Nesting Loggerhead Tracks (Michael Wauson)

Flipper elbow joint mark

Carapaces drag marks

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Figure 3. Loggerhead nesting image (Preserve Hawai’i).

Over their lifespan, loggerheads contend with a wide variety of predators. In the

nest, loggerheads are vulnerable to crabs, ants, canids (including domestic dogs, foxes

and coyotes), boars, raccoons, and both domestic cats and bobcats (Engeman et al. 2006).

As the eggs hatch and the hatchlings are on their way to the water, they contend with the

predators listed above as well as snakes, crows, gulls, and several species of raptors.

Once in the water, hatchlings are vulnerable to birds and large predatory fish. As the

turtles grow, their predator list shrinks to killer whales (Orcinus orca) and a few species

of sharks such as tiger sharks (Galeocerdo cuvier) (Heithaus et al. 2008).

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Conservation Issues

Loggerhead sea turtles are listed as vulnerable by the International Union for

Conservation of Nature (IUCN) with a population that is declining. The main reason for

this decline is human activity (IUCN 2017A). Humans harvest loggerheads for

consumption (A), but commercial fishing (longline and trawling) also results in

loggerhead bycatch (B). Other human-generated threats include marine deposition of

garbage (C), pollution from agricultural and automotive runoff and oil spills (D), beach

changes, which includes artificial lighting, coastal armoring (sea walls, rock revetments,

and sandbags), beach erosion (E), human beach activities and human introduced

predatory invasive species (F), and climate change (G) (U.S. Fish and Wildlife Service

1978).

A) Consumption

Human consumption has had a significant effect on loggerheads and other sea

turtle species in North America. multiple studies in Baja California Sur, Mexico,

focused on human consumption of loggerheads. One found that 45.5% of 1041

loggerhead carcasses located had been harvested for meat (Mancini and Koch

2009). The consumption of turtle meat seems to be related to local cultural

factors, as it was consumed most often during the Christian fasting period of

Lent (Mancini and Koch 2009, Peckham et al. 2008). Mancini and Koch (2009)

and Peckham et al. (2008) also found multiple local, regional, and international

black-market areas developed for the sale and consumption of sea turtle meat.

Human consumption of turtles is not limited just to North America but is also

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practiced in many countries including Madagascar, Mozambique, and South

Africa to list a few (IOSEA Marine Turtle MoU 2013).

B) Commercial Fishing

Two activities associated with commercial fisheries that result in significant

negative effects on loggerhead populations include long-lining and trawling. In

2000, an estimated 200,000 loggerhead sea turtles were caught on the hooks of

longlines, resulting in tens of thousands of moralities (Lewison 2004). Longlines

used for swordfishing have the largest effect on loggerheads due to their

placement near the surface of the water column (Taylor and Haplin 2008). The

consequences of being caught on a longline can vary. If the turtle is unable to

reach the surface, it will drown. If it does not drown, the long-term effects of

being hooked in the mouth or flipper are relatively unknown but could be

disfigurement and reduced mobility.

Trawling has a major impact on loggerhead populations. In the late

1980’s, Turtle Excluder Devices (TEDs) were developed and implemented by

the U.S. and numerous other fishing fleets. TEDs dramatically decreased

loggerhead losses, but fishermen and nations that do not implement TEDs are

still a threat to loggerheads (Crowder et al. 1995). It is estimated that 30,000

loggerheads are caught by trawlers in the Mediterranean Sea per year, with a 25

percent mortality rate (Sala et al. 2011).

C) Marine Deposition of Garbage

Marine deposition of garbage has serious consequences for marine life. For

example, at least 267 species of organisms are known to be negatively affected

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by plastic debris, and its accumulation over the decades has resulted in the

deaths of millions of animals each year (Moore 2008). In the case of sea turtles,

they apparently mistake some plastic items for jellyfish, which are among their

primary food sources. Oceanic juveniles are particularly vulnerable to death

from ingested plastics. Pham et al. (2017) found 20 of the 24 sampled

loggerheads had consumed garbage containing plastic debris; the animals

averaged 15.83 (S.E. ± 6.09) items of plastic in their stomachs. In total the items

had a mean dry weight of 1.07g (S.E. ± 0.41), an amount that can prove fatal

(Pham et al. 2017).

D) Marine Pollutants

Marine pollutants have a substantial effect not only on sea turtles directly, but

also on their food sources. Many of the pollutants affecting aquatic life come

from agricultural and automotive runoff as well as from oil spills (Ley-Quiñónez

et al. 2011). The chemicals from runoff result in bioaccumulation and

biomagnification of pollutants in the prey items of loggerhead turtles, which

results in possible illnesses and diseases to the turtles during the course of their

lives (Maffucci et al. 2009). A potentially lethal or debilitating illness is

fibropapilloma tumors, which develop predominately in fibrous tissue, but can

affect all kinds of soft tissues; the tumors have recently been linked to the

chelonid herpesvirus 5 (Rossi et al. 2015) and are suspected to cause debilitating

cutaneous infection (Lackovich et al. 1999). Oil spills, on the other hand, have

more immediate effects on turtles such as increased susceptibility to infection,

and can result in severely altered blood chemistry when oil is ingested. Oil spills

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also result in the loss of potential nesting sites when oil washes onto beaches

(Lutcavage et al. 1995, Lauritsen et al. 2017).

E) Beach Changes

Beach changes such as coastal armoring such as sea walls, and erosion have a

dramatic effect on loggerhead nesting. When coastal armoring is built to protect

human coastal infrastructure, the altered beach structure results in fewer

successful nesting emergences compared to natural dune areas (Mosier and

Witherington 2001). Because loggerheads are philopatric – females return to

nest on the beach where they hatched – beach erosion (natural or human

influenced) is another threat (Stiebens et al. 2013). It can take a loggerhead 33

years to reach sexual maturity; thus, the beach where a female hatched could be

gone or modified in such ways that she is unable to nest where she was hatched.

This forces the female to choose between an unknown beach that may not be

conducive to the survival of her offspring and risking nesting on the modified

armored beach (Mosier and Witherington 2001).

F) Other Human Beach Activities and Invasive Species

Beach activities and invasive species are interrelated in that domestic and feral

dogs and cats are known to dig up nests and eat hatchlings (Turkozan et al.

2003, Hilmer et al. 2010). Human and animal activity at night can keep nesting

females from leaving the ocean to nest or disrupt a female while she is laying

her eggs or digging her nest to the point where she leaves the beach. Another

threat is recreational equipment such as chairs on the beach, boats on the beach

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or in the water, and other debris that can deter nesting females (U.S. Fish and

Wildlife Service 1978).

G) Climate Change

Climate change exacerbates some of the issues listed above, especially beach

erosion and human attempts at coastal armoring in the face of rising sea levels

and larger storms. One of the primary effects of climate change is increased

mean annual temperatures. As the temperature of the beaches increases, so does

the ratio of female to male turtles that are produced (Abella et al. 2007). This is

because loggerheads like most turtles, sex is based on temperature-dependent

sex determination (temperature of each egg in the nest will determine the sex of

that individual), eggs incubated below 27.7 Celsius will be male and anything

over 31 Celsius will produce females. Anything between that range with

produce either or. As the temperatures increases, it forms a potential genetic

bottleneck as the sex ratio becomes more and more skewed towards females;

however, there is evidence that as temperatures rise, the nesting season will

begin earlier in the year, perhaps mitigating this effect (Thaler and Fuentes

2016, Weishampel et al. 2008).

Coyotes

Natural History of Coyotes

Coyotes (Canis latrans) are native to the plains and southwest deserts of North

America, but over the last 150 years they have spread across the United States (Bozarth et

al. 2011). Moving east, they took two primary paths: the northern front went through the

Great Lakes region and the southern front moved through the Gulf States (Bozarth et al.

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2011). As they moved, the northern and southern groups contended with different

competitors and environmental pressures. In their original home ranges, coyotes had to

cope with timber wolves (Canis lupus), mountain lions (Puma concolor), black bears

(Ursus americanus), and brown bears (Ursus arctos). As they moved east, the northern

group encountered and interbred with the Great Lakes population of timber wolves,

according to DNA evidence (Bozarth et al. 2011). In contrast, as they traveled east, the

southern front no longer had to contend with timber wolves but encountered the red wolf

(Canis lupus rufus), a subspecies native to the southeastern United States (IUCN 2017B).

Red wolves resemble coyotes in body size, prey preference and social group behavior

(U.S. Fish & Wildlife Service 2016). Thus, there is a large niche overlap between the two

species, and they are known to interbreed (Wayne and Jenks 1991).

Coyotes are relatively small canids weighing between 9 to 22.7 kg. Their lifespan in

the wild is 6-8 years, on average (Bekoff 1977). Carlson (2008) found that coyotes are

usually monogamous, maintaining pair bonds for many years. They are reproductively

capable as early as ten months of age, but adults (34 months or older) have the highest

fecundity. They have from three to seven pups per litter on average. Pups are usually

born between March and May after a 60 to 63 day gestation period (Carlson 2008) and

leave the parental territory as early as six to nine months of age or remain as subordinates

in the pack. Both parents protect the territory and provide food for the pups (Gier 1968).

Coyote pack size varies based on food availability. The more abundant the food

source, the larger the pack tends to be. A pack is made up of the alpha breeding pair,

young of the alpha, and other individuals (not offspring of the alpha pair) that have been

accepted into the pack (Bekoff and Wells 1980). Usually only the alpha male and female

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breed (Carlson 2008). There seems to be no correlation between pack size and territory

size (Bekoff and Wells 1986).

Coyotes are omnivores with a broad diet that includes small mammals, birds,

livestock, pets (cats and dogs), fruits, vegetables, carrion, and eggs (Pennsylvania Game

Commission 2014). In pairs or a pack, coyotes can take down large ungulate prey such as

mule deer (Bowen 1981). Mountain lions and wolves are the two largest predatory threats

to coyotes in terms of numbers of animals killed in their native range (Merkle et al. 2009;

Washington Department of Fish & Wildlife).

Coyotes are considered a nuisance and invasive species in South Carolina; SCDNR

encourages the hunting of coyotes (SCDNR 2015). The coyotes’ ability to adapt to a

wide range of diets and habitats makes them very versatile predators, and is why it is

believed that coyotes can fill the niche left vacant with the elimination of the region’s top

predator, the red wolf. The coyote’s ability to exploitation food options in its

environment is not limited to wild game, but can also extend to domestic animals,

resulting in a substantial financial problem for farmers. In 2000, coyotes were responsible

for a loss of over ten million dollars due to calf predation alone in the Eastern United

States (Houden 2004).

Coyotes can be significant predators on sea turtle nests. For example, on the Baja

California Peninsula in Mexico, 81.4 percent of monitored loggerhead nests were

depredated by coyotes (Mendez-Rodriguez and Alvarez-Castaneda 2016). In the

conclusion of that paper, Mendez-Rodrigues and Alvarez-Castaneda (2016) state that

coyotes should be considered an important predator of sea turtles.

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The Study Site

History of Tom Yawkey Wildlife Center

South, North, Cat and Sand Islands make up the Tom Yawkey Wildlife Center off

the coast of Georgetown, South Carolina (Figure 4). The preserve was established in

1976 by Tom Yawkey, the former owner of the Boston Red Sox. The preserve is 97.12

K𝑚2 (24,000 acres) (SCDNR Public Lands 2016) in area. It includes marshes, wetlands,

maritime forests and beaches.

The preserve has a rich history dating back before colonial times with the Pee

Dee, Samtee, Sampit, See Wee, Waccamaw, and Winyah Native Americans inhabiting

the area. The Archaeology and Anthropology Institute at University of South Carolina

has dated one of the sites on Cat Island going back as early as 1500 B.C. (SCDNR 2004

Tom Yawkey Wildlife Center).

During the Civil War, South, Cat and North Islands were fortified with forts and

batteries (SCDNR 2004). A few of the military landmarks can be seen today on Cat and

North Islands. After the war, Confederate General Edward Porter Alexander, Bill

Yawkey and Joseph Wheeler bought land on North and South Island and turned it into a

waterfowl hunter’s paradise. Powerful men of the time, including President Grover

Cleveland, frequented the islands for the rich hunting grounds (SCDNR 2004). Bill

Yawkey eventually became the sole owner of the islands and upon his death, he

bequeathed the land to his nephew and namesake of the preserve, Tom Yawkey (SCDNR

2004). In the late 1930’s, Tom began to change the focus of his land from hunting to

conservation aimed at creating a waterfowl refuge. Tom Yawkey died on July 9th, 1976.

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His will bequeathed his South Island Plantation to the State Wildlife and Marine

Resources Department, which cares for it to this day (SCDNR 2004).

Figure 4. The Tom Yawkey Preserve divided into its four islands (Eskew 2012).

History of Loggerheads on South Island

The first survey for loggerhead sea turtles on South Island beach was in 1977.

Since that time, there have been continuous conservation and management plans in place.

South Island beach is 5.88 km long and averaged 241 loggerhead nests per year from

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2015-2018. Over the last three years (2015-2017), an average of 4,140 eggs on South

Island beach (15.86 percent of the eggs laid per season) have been depredated each year

by coyotes. A mean of 69 eggs are destroyed each time a coyote raids a nest (SCDNR

unpublished).

Three apex terrestrial predators, coyotes, bobcats (Lynx rufus), and American

alligators (Alligator mississippiensis) call the Yawkey preserve home. Since 2015, there

have been no documented bobcat or alligator depredations of loggerhead nests on South

Island beach (SCDNR unpublished). SCDNR does however report that in 2009 and 2013,

there were egg and nest losses on South Island beach due to “other” causes that did not

fall under the usual ghost crab, coyote, research, tidal, or racoon losses (SCDNR 2017).

History of Loggerhead and Coyote interactions and conservation techniques in the Yawkey

Preserve

Coyotes have become major predators on loggerhead eggs on the Yawkey Islands

since their first appearance in 2006 (Eskew 2012). As of 2009, they were responsible for

52% of loggerhead egg losses in the preserve (SCDNR 2010). The methods that have

been tried to protect loggerhead nests on the Yawkey Islands from coyote depredation

have met with varying degrees of success. Techniques employed include using high-

pitched sounds near turtle nests, but that showed no detectable effect on depredation

levels (Pers. Comm., Jamie Dozier, Certified Wildlife Biologist and Project Leader at the

Tom Yawkey Wildlife Center). Nightly patrols by humans worked well to deter coyote

depredation but resulted in a massive number of man-hours and, as a consequence, were

expensive and could not be sustained (Eskew 2012). Caging the nests the morning after

the eggs are laid is extremely effective at dissuading coyotes and raccoons, but this

method still leaves the nest vulnerable the night the eggs are laid (Pers. Obs.). It is

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believed that several coyote packs occupy areas in the Tom Yawkey Preserve but that a

single pack patrols the South Island beach and that the beach constitutes most of their

territory (Pers. Comm., Jamie Dozier). Removal of this coyote pack is the most recent

control attempt and has had very limited success; it required a large number of man-hours

due to the terrain and failed because of the canids’ rapid learning to avoid traps (Pers.

Comm., Jamie Dozier).

The Present Project

I proposed to test a novel method to reduce coyote depredation on sea turtle nests on

the Yawkey Islands based on research by Merkle et al. in 2009 on the timber wolves

reintroduced to Yellowstone National Park in 1995, and their interactions with coyotes.

That study provided an important opportunity to understand the competitive interactions

between coyotes and timber wolves. Competition can be broken down into two main

components: interference and exploitative (Smallegange et al. 2006). Interference

competition occurs when organisms directly vie for resources. One type of interference

competition is intraguild competition, where one competitor kills and sometimes eats the

other, a form of predation. For example, Merkle et al. (2009) documented 337

interactions where wolves dominated (i.e., killed or forced coyotes to leave the

immediate area) in 91 percent of the interactions and proved lethal to coyotes in 7 percent

of those meetings (Merkle et al. 2009).

Exploitative competition results from organisms indirectly competing with other

species for resources and consuming those resources to the point where they are denied to

other species. For instance, territory marking by wolves where coyotes in these areas of

high wolf use exhibited decreased rest and increase the time spent in vigilance activities

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(Switalski 2003, Lang et al. 2013). Exploitative competition may be the result of

interference competition with a particular species. In the studies above (Switalski 2003)

the coyotes initially had more confrontations with wolves, but as time passed, the coyotes

were seen less and less near wolves. This could have been due to a greater food

availability with the change in seasons, or because interference competition needs to be

present to create exploitative competition. To keep the one-sided (exploitative)

competition in balance an animal may require the competitor to physically be present.

The level of exploitative competition between animals varies in locations due to

dietary overlap and prey distribution and abundance (Fonju 2011). This was seen in a

study in Alaska where coyotes and wolves were studied but wolves primarily fed on

moose and coyotes fed on small mammals; with less dietary overlap there was less

competition between the two organisms (Thurber et al. 1992). In the North Fork area of

northwestern Montana, however, where dietary overlap was higher, there was an

observed decrease in the coyote population as the wolf population increased, suggesting a

higher level of competition (Arjo et al. 2002). Another observation involving canids in

exploitative competition is between African wild dogs (Lycaon pictus) and spotted

hyenas (Crocuta crocuta), where high dietary overlap resulted in a negative correlation in

wild dog and hyena densities (Creel and Creel 1996).

These studies were central to my understanding of exploitative competition between

coyotes and wolves, and I hypothesized that lessons learned from them could be applied

to the conservation of loggerhead sea turtles. Thus, I simulated wolf “presence” and

activity on South Island beach using wolf urine dispensers to test whether wolf urine

would deter coyote depredation of loggerhead sea turtle nests.

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Methods and Materials

Layout and Execution

From May 11th to May 17th, 2018, I established control, partial control and

treatment areas on South Island beach at the Tom Yawkey Wildlife Center, S.C. There

were seven 200-meter long control areas, thirteen 100-meter long “partial-control” or

“buffer” areas, and seven 200-meter long treatment areas. Areas designated as partial

controls were required between the treatment and control sites because it was unclear

how far the wolf urine scent would disperse.

Each treatment and control area required 50 wolf urine dispensers which were

constructed following the manufacturer’s instructions (Maine Outdoor Solutions). Each

dispenser consisted of one plastic bottle containing 44.36 mL of wolf urine attached to a

25.4 cm wooden post using hardware provided by the supplier. Posts were placed 4

meters apart, with the container section on the seaward side and the wooden support post

facing the landward side. The dispensers formed a 4100 m line running on top of the first

dune line, and parallel to the shoreline. A transect at each end of the treatment group ran

perpendicular from the dune line down to the “king tide” line (which marks the extent of

higher than normal tides brought on by specific alignments of the moon and sun) (see

Appendix 1). The perpendicular line also was furnished with dispensers 4 m apart, per the

manufacturers’ instructions. In some cases, there was only room for one dispenser to be

placed before the king tide line, but in other areas, up to three were set. Stakes were

placed every 50 meters to indicate the type of treatment area (treatment, control, or partial

control) a nest was discovered in.

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The South Carolina Department of Natural Resources Turtle Technician Team

collect and provided all the data dealing with loggerhead nest dates, location, depredation

events (including predator identification), counts of eggs, nests depredated, and nest

losses. Data collection for my work started when the first loggerhead nest appeared on

the beach after the dispensers were in place. The team would arrive on the beach just

before sunrise or, due to tide variability, an hour or two later when the high tide passed.

The team used four-wheelers to patrol the length of South Island beach in search of

“turtle crawls” as well as predator prints. When a crawl was located, the team drew a

perpendicular line through the turtle’s trail above the high tide line to ensure that the

crawl was not logged twice. The team then followed the crawl to determine whether a

nest was constructed.

If a nest was located intact, it was caged using a metal mesh box that enclosed the

nests on the tops and sides with spacing to allow hatchlings to pass through. For

depredated nests, the team removed all broken eggs from the nest and searched the

surrounding area for broken eggs. Once all the depredated eggs were counted, the

remaining intact eggs were removed from the nest, cleaned and relocated to a nearby

man-made nest at the dune line and buried about one meter down into the sand. The team

then determined the predator by the paw prints left in the sand. The teams were trained

and used diagrams to compare and identify prints. The GPS location of the original and

relocated nests, along with the egg counts of depredated nests, were recorded. I traveled

to the preserve bi-weekly to collect the data from the technician team and to inspect and

fill the urine dispensers.

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I visited to the beach to collect the data and refill/ replace dispensers between

May 17th to August 11th. The dispensers were filled at 30-day intervals with 44.6 mL of

urine following the manufacturer’s guidelines until July 14th when they began to be filled

biweekly. I changed the filling interval because the urine in the dispensers lasted

approximately 9 days, not 33 days as expected based on the manufacturer’s instructions.

At the bottom of each filled vial, moist colored sand was found that seemed to hold the

scent of the urine after the rest of the liquid evaporated. Between visits to the island,

dispensers were sometimes lost either due to burial from beach sand movement or to tides

and wind. This loss happened to about five dispensers per section. I searched for and

when possible restored these but if the dispensers could not be located, new ones were

constructed to replace them.

Data I analyzed but not collected by the turtle techs included high and low tide

levels (m), mean daily temperatures (C), percent lunar visibility, nocturnal atmospheric

conditions (clear sky, overcast, mixed), whether there was nocturnal rain, and nocturnal

wind direction. This data was analyzed to determine if there is an ideal time to perform

night patrols in regards to when loggerheads are most likely to nest or coyotes to

depredate. All data listed above were from May 17th to August 9th between 2015 to

2018. In addition, I analyzed loggerhead nest locations, depredation events by an

identified predator, all these forms of data were collected by the turtle techs. The wind

direction, mean daily temperature, atmospheric conditions, and precipitations data came

from Weather Underground. The tidal data came from Tides4Fishing and lunar data from

Timeanddate.com.

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Statistical Analysis

To test the effect of wolf urine on the depredation of loggerhead nests, I

initially broke down the data into two sets, 9 days and 30 days. I broke it down this way

because urine on the Yawkey Islands during the summer evaporated in 9 days. The 30-

day blocks were the intervals when I filled the dispensers. Partial control areas were

initially analyzed as separate entities but were found to be statistically indistinguishable

from the control areas using a Fisher Exact Test. Based on that, I combined the partial

control data with the control data forming the Total Control group. From there, I

compared the two-groups (Total Control and Treatment) at the 30-day interval and then

at the 9-Day interval using a Chi-Squared test and Fishers Exact Test respectively.

For the below tests, I compared 2018 data with the combined data for 2015

through 2017 to determine if 2018 was unique. If the tests before showed no difference I

combined the data of the four years to determine the effects of some climate elements and

tides affect loggerhead nesting behavior. I used a Kruskal-Wallis Test to determine if

atmospheric conditions (overcast sky, clear, or mixed (50% overcast)) affected the

number of loggerhead nests laid per night. I used Mann-Whitney U tests to determine

whether nightly precipitation and wind direction (landward or seaward) affected the

number of nests laid. I used Spearman’s rho tests to determine whether there was a

correlation between: mean daily temperature and the number of nests laid; mean daily

temperature and the number of depredated nests per night; and percent moon visibility

and the number of nests laid.

To determine the effects of the same climate elements had on coyote depredation

events on loggerhead nests. I again ensured I could combine the 4 years but excluded the

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treatment area data for 2018. I then used Chi-squared tests to determine if nocturnal wind

direction affected the number of nests depredation by coyotes per night, if nocturnal tide

types affected the number of nests depredated by coyotes per night, if nocturnal rain

affected the number of nests depredated by coyotes per night, and if nocturnal

atmospheric conditions affected the number of nests depredated by coyotes per night.

Results

Wolf Urine Effectiveness

The proportion of nests made and depredated during my data collection did not

differ between control and partial control conditions (Fisher Exact Test, p=0.2718, ns)

(Table 1). That result allowed the two groups to be combined into a single entity, “total

control”.

Table 1. Comparison of all coyote depredation events in control and partial control areas over

the entire experiment, based on 30-day intervals between dispenser refilling’s (Fisher exact test,

p=0.2718, ns)

From there I determined there was no difference in number of nests depredated by

coyotes between the total control and the treatment areas (Fisher Exact Test, p=1, ns)

(Table 2).

Non-depredated Depredated Total

Control 39 12 51

Partial Control 15 9 24

Marginal Column

Totals

54 21 75

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Non-Depredated Depredated Total

Total Control 54 21 75

Treatment 30 12 42

Totals 78 33 117

Table 2. Comparison of number of loggerhead nests made and coyote depredation events between

the total control and treatment areas for the entirety of the experiment (30-day time interval)

(Fisher exact test, p=1, ns)

I once more made a comparison, this time between depredation rates during the 9-

day interval following a refill. I confirmed that again control and partial control areas

could be combined, this time for 9-day intervals (Chi-Squared, χ2=.0078, df=1, p=0.929,

ns) (Table 3).

Non-Depredated Depredated Total

Partial Control 8 5 13

Control 12 8 20

Totals 20 13 33

Table 3. Table shows that for 9-Day grouping, control and Partial control can be combined to for

a Total Control again using a Chi-Squared Test. χ2=.0078, df=1, p=.929

Finally, I compared the total control areas versus the treatment areas for the 9-day

interval. I found a no significant depressing effect of the urine on coyote nest

depredations in the treatment areas compared to the Total control areas (Fisher Exact

Test, p= 0.0759, ns) (Table 4).

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Non-Depredated Depredated Total

Total Control 20 13 33

Treatment 10 1 11

Totals 30 14 44

Table 4. Shows the 9-Day grouping comparing Total control nest and depredations to the

Treatment using a Fisher Exact Test (p=.0759).

Other Variables Tested

I found no differences between 2018 and the prior three years for either number

of nests laid or number of nests depredated. (Chi-squared test, χ2 = 0.012, df= 1, p=

0.913, ns) (Table 5). Since they were not statistically distinguishable from one another,

the nesting data and depredation data were combined in later tests.

Nests Laid Depredation Events Total

2015-2017 659 160 819

2018 160 38 198

Totals 819 198 1017

Table 5. Comparison of loggerhead nest data and coyote depredation event data for the 2015

through 2017 season versus 2018 season (Chi-square, χ2= 0.012, df=1, p= 0.913, ns)

Variables That May Affect Loggerhead Sea Turtle Nesting Behavior

Across all four years (2015 through 2018), none of the tested variables had an

effect on, or correlation with, the number of loggerhead nests laid per night on South

Island beach.

• Nocturnal atmospheric conditions (Kruskal-Wallis Test, χ2 = 4.639, df= 2, p=

0.098)

• Mean daily temperature (Spearman’s rho, P =.023, p=0.569, ns)

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• Nocturnal precipitation (Mann-Whitney U Test, χ2 =-1.298, p=0.194, ns)

• Nocturnal wind direction (Kruskal-Wallis Test, χ2 =.809, df=2, p=0.667, ns)

• Moon phase group (Kruskal-Wallis Test, χ2 =2.233, df=3, p=0.525, ns)

• Nocturnal tide types (Chi-squared, χ2 =0.0, df=1, p=1, ns)

Variables That May Affect Coyote Depredation of Loggerhead Sea Turtle Nest

Behavior

Across all four years (2015 through 2018) but not including data from the

treatment area in 2018, none of the tested variables had an effect on, or correlation with,

the number of loggerhead nests laid per night on South Island beach.

• Nocturnal atmospheric conditions (Chi-squared, χ2 = 3.41, df= 2, p= 0.1818, ns)

• Mean daily temperature (Spearman’s rho, χ2 =0.094, p=0.101, ns)

• Nocturnal precipitation (Chi-squared, χ2 =0.22, df=1, p=0.6892, ns)

• Nocturnal wind direction (Chi-squared, χ2 =1.07, df=2, p=0.5857, ns)

• Moon phase group (Chi-squared, χ2 = 5.18, df=3, p=0.1591, ns)

• Nocturnal tide types (Chi-squared, χ2 =.33, df=1, p=0.6468, ns)

Discussion

Wolf Urine as a Deterrent

The wolf urine had no effect on coyote depredation rates on South Island beach

when I followed the manufacturer’s guidelines and filled the urine dispensers every 30

days (Table 2). Once I determined that the urine evaporated in 9 days, however, and

repeated the analysis, I found that the urine still did not depress the depredation events

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significantly (Table 4) (Appendix 2). The reason for this I believe is the evaporation of

data as a result of only being able to analyze 44 nests compared to the 117 nests

deposited during the experimental treatment. If we take the proportions from Table 4

(Table 6) then extrapolate that to the 117 nests available. Using a Fishers Exact Test we

get a different story (Table 7). There can be some error expected in this but we can triple

the number of nests depredated in the treatment area and still have a significant

depression in depredations in the treatment area. This shows that on South Island beach

on the Yawkey Islands, as long as timber wolf urine is present, it potentially could be

used as a deterrent to coyote depredation of loggerhead sea turtle nests. This in turn

supports my hypothesis that timber wolf urine can be used as a deterrent to coyote

depredation of loggerhead sea turtle nests.

Non-depredated Depredated

Total Control 45% 30%

Treatment 23% 2%

Table 6. Shows the proportions from Table 4.

Non-Depredated Depredated

Total Control 53 35

Treatment 27 2

Table 7. Shows the extrapolated data for the nests made using Table 6 proportions and then

comparing the Total Control to the Treatment area (Fisher Exact Test p=.001).

I suspect the mechanism behind the depression in depredation events to be

exploitative competition between the coyotes and the simulation of wolf presence even in

the absence of interference competition. The coyotes on South Island have had no contact

with wolves since their arrival in 2007 and probably for many generations prior. Their

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behavior, though, resembles what Merkle et al. (2009) observed watching coyote

interactions with wolves in Yellowstone National Park. The avoidance behavior shown

by the coyotes with regard to wolf territories in Yellowstone as well as the high vigilance

displayed when present in a wolf territory, can be inferred as occurring in the treatment

areas of this experiment when urine was present.

There much evidence that urine can convey all kinds of information about the

depositor. Porton’s (1983) study on bush dog (Speothos venaticus) urine-marking

suggests that urine can indicate the sex, and potentially the identity, of the depositor.

Using wild-derived house mice (Mus musculus domesticus) Zala et al. (2004) found that

urine-marking may be an example of the “Mister Good Genes” model, showing evidence

that it may act as an honest display of health and condition. Finally, Jones and Nowell

(1973) suggested that male mice (Mus musculus domesticus) may be able to determine

social status from the amount of testosterone present in an individual’s urine. Gosling

and Roberts (2001) took this a step further by stating that in many terrestrial mammals

the receiver smelling the scent-marking may be able to detect intrinsic properties of the

donor and may be able to identify past competitors or learn information about future

competitors. They also suggested that scent-marking density and refreshment rate could

provide valuable information about the depositor’s competitive ability because of the

increased energetic costs of traveling and increased risk of predation during marking and

traveling (Gosling and Roberts 2001).

In addition, the competing countermarks hypothesis states that the urine-mark that

is on top of a countermark (scent marking on top of or near another scent mark) will be

preferred by females of the same species (Rich and Hurst 1999). Counter marking has

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been seen in a plethora of mammals from house mice (Mus musculus domesticus) to lions

(Panthera leo) to ring-tailed lemurs (Lemur catta) and sugar gliders (Petaurus breviceps).

Rich and Hurst (1999) focused their experiment on house mice and found evidence to

support the competing countermarks hypothesis. This is important because it supports

Gosling and Roberts (2001) statement regarding the energetic costs that are required to

continuously mark a territory.

Because the coyotes on the Yawkey Islands have never been exposed to wolves,

we cannot know how they might interpret the urine. It may have been perceived as

coming from an unfamiliar coyote pack. Since the urine from my experiment was from

multiple wolves and sexes, the urine dispensers could have been perceived as

countermarks (Rich and Hurst 1999) or as a large pack marking its territory, as a coyote

group might do (Bowen and Cowen 1979). Combining the perception of a large pack

with the fact that for the nine days after the dispensers were filled, they continually

contained urine in its liquid form (not dissolved in a substrate) might have made it seem

as if there was a constant competitor presence in the area.

However, coyotes can presumably recognize urine deposited by their own species.

Thus, the Yawkey coyotes could have interpreted it as having been deposited by an

unknown form, perhaps a canid, and possibly one that poses a threat. Therefore, even

given a lack of direct experience with wolves, coyotes may retain the capacity to

recognize unfamiliar canid urine as possibly belonging to wolves, as opposed to another

species such as the gray (Urocyon cinereoargenteus) or red fox (Vulpes vulpes). The

large number of urine dispensers outlining the “territory” (treatment area) in this

experiment should mimic urine deposition behavior shown by wolves in Yellowstone

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National Park and elsewhere because their scent marking frequency is normally denser on

the exterior of their territories than in the interior (Sillero-Zubiri and Macdonald 2001,

Peters and Mech 1975, Bowen and Cowen 1979).

Wolf urine, as is true for that of many other, if not all, canids, contains sulfur-

bearing pyrazine analogues that have been identified as a type of semiochemical called a

kairomone (Osada et al. 2013). These pyrazine analogues are detected by the

vomeronasal organ, which is part of the tetrapod olfactory system (Romer1970); this

organ is important in the detection of pheromones, chemicals used to influence behavior

in conspecifics, as well as volatile odorants from other species (Osada et al. 2015).

Kairomones are interspecific chemical signals that can inform potential prey items of the

presence of a carnivore and can elicit avoidance and freezing responses in mice, deer and

cattle exposed to them (Osada et al. 2013, Osada et al. 2015).

Again, it is possible that the coyotes interpreted those pyrazines as arising from other

coyotes because pheromones are also semiochemicals. They transmit information about

an individual organism’s sex, health, social status, etc., and in the case of this experiment,

they could have caused resident coyotes to become wary of the possible presence of a

large number of conspecifics regularly invading their territory.

One type of information that might be gained from the urine is that there is a

predator in the vicinity (Osada et al. 2015). This has been observed with lab mice in the

presence of urine from predators that neither they nor their ancestors had been exposed to

for at least 70 years and, assuming 4 generations per year, at least 280 generations (Papes

et al. 2010). Coyotes have a well-developed vomeronasal organ (Adams and Wiekamp

1984) and exhibit the Flehmen response, which entails getting the mouth and airway into

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a certain position to ensure scents are pulled into the vomeronasal organ (Ewer 1973).

The results of my experiment, indicate that coyotes were able to detect the wolf

kairomones and therefore avoided (at least during the 9-day period when liquid urine was

present) the treatment areas.

Further insight can be gained from this apparent avoidance behavior by

referencing a study on competition types (exploitation, interference, cannibalism and

intraguild) in scorpions. Polis (1988) found that the closer in size two individual

scorpions were, the greater the level of exploitative competition and the smaller the level

of interference competition that existed between them. This is suspected to be because

there is a greater potential for harm if an altercation arose between the two organisms.

The inverse of this is that there is less exploitative competition but more interference

competition (potentially including intraguild competition) the greater the size difference

between the organisms. I suspect that without the wolves to physically dominate the

beach, the coyotes focused on plundering the control areas and avoided the treatment

zones resulting in exploitative competition.

Without the actual threat of wolves to reinforce the danger the urine implied, the

depressive effect the urine had on coyote depredation may have been only temporary. I

also doubt that covering an entire beach with wolf urine would be effective because, for

all intents and purposes, the urine is a bluff, and covering an entire beach with urine may

force the coyotes to try and hunt in the protected areas and ultimately discover the bluff.

These animals are by no means incompetent, and the habitualization of the urine scent I

suspect will only be a matter of time. However, there are a number of modifications to

my technique that may increase its effectiveness.

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When using urine to deter coyotes, I believe it would be more efficient to use

dispensers that hold at least twice as much as the dispensers from this experiment (44.36

mL) to ensure the presence of urine over a longer time and to reduce refilling to every 21

days or more depending on the container size. Sharpe (2015) suggested that mammals

may extract size information based on the height of the urine deposited. Taller stakes,

around 45 cm in length may increase the effectiveness of the urine as a deterrent since the

coyotes may believe that a larger canid resides in that portion of the beach. It is also

necessary to increase the height of the dispensers because sand movement on South

Island beach caused many of the dispensers to be found at ground level, or to be partially

to completely buried. However, the stakes must be made pliable or low enough to ensure

that they do not impede the turtles as they crawl up the beach to nest. For future

investigations, it would be interesting to determine if it is the novelty of the urine that

deters the coyotes rather than the type of urine itself. I would recommend testing this with

either of the two other predator urine commercially available (bear and mountain lion). If

either or both predator urines work, then potentially switching out the urine in the

dispensers seasonally may prevent or slow the habituation of the coyotes to its presence.

Loggerhead Sea Turtle Nesting Analysis

The fact that none of the naturally occurring potential influences that I tested

(atmospheric conditions, mean daily temperature, nocturnal precipitation, nocturnal wind

conditions, moon phase grouping and nocturnal tide type) had an effect on loggerhead

nesting behavior was not surprising. Loggerhead turtles can be seen searching the

beaches at night looking for good nesting locations. If they are not successful, that is, if it

is a false crawl, the turtles return to the ocean but presumably try again the following

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night or soon thereafter (Pers. Obs). Thus, none of the natural phenomena I tested appear

to predict when a female turtle is more likely to come ashore to nest.

Coyote Depredation of Loggerhead Sea Turtle Nest Analysis

I initially believed that a landward wind, a lack of precipitation, and greater moon

visibility would help the coyotes locate fresh turtle nests. This was believed because most

of the island’s coyotes live inland, and hunting with greater visibility in a clear night

should lend itself to scavenging. However, no naturally occurring external influences I

tested predicted or correlated with coyote depredation events. As mentioned in the

introduction, it is believed that a single pack patrols the South Island beach and that the

beach constitutes most of their territory (Pers. Comm., Jamie Dozier). As a result of being

restricted to this thin stretch of land, and because the nests are covered and protected

from depredation at daybreak by the sea turtle technicians, the only time the coyotes have

access to such an easy food source is when they patrol the beaches nightly. The lack of

predictability or correlation with environmental factors may be a result of this particular

system at the preserve and should be evaluated again in a location comparable to the

Yawkey Islands (no to little human presence on beach minus turtle patrols) but with a

coyote pack that has a territory that is not made up of primarily beach. This will allow

that pack to choose between hunting inland versus patrolling the beach and will give a

clearer picture on the effect of natural external influences on coyote hunting.

Final Recommendations

For the Yawkey Islands and locations similar to them, the best conservation tools

to deter coyote depredation on the nests the night they are laid is a deterrent that is

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relatively cheap, and will work for the entirety of the nesting season. The system I have

described and tested covered 1400 meters of beach (treatment area only) and cost

$1,840.05. If the urine dispensers are of higher quality and can be reused from season to

season, the costs will be reduced further. The seasonal costs for just urine would be about

$97.08 per 100 meters of beach with better pricing available with larger orders. The cost

for refilling the dispensers can be mitigated by using dispensers of greater height and

volume, which would make them easier and faster to refill and decrease the total number

of refills required during the season. If the refilling dates are staggered, so that only one

section needs to be refilled each day, it would cut down the daily time requirement as

well. The refilling could also be done by volunteers since no permit is required in South

Carolina, and potentially other states, as they are not directly interacting with the turtle

nests.

The urine resulted in a 90.9% reduction in nest depredation in the treatment zones

compared to the total controls. The urine could protect over 1,995 eggs per season on that

single beach, if only half of South Island beach is covered with urine dispensers, and

assuming the average depredation rates from the last four years. With two more nesting

beaches just on the Yawkey Islands, and many more throughout the country, this

technique could be a vital tool in the conservational arsenal for protecting loggerheads

and potentially other sea turtles from further coyoted depredations.

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sea turtles following sea surface warming. Global Change Biology. 10(8)

Wood, D.W., Bjorndal, K.A., (2000) Relation of temperature, moisture, salinity, and

slope to nest site selection in loggerhead sea turtles. Copeia. 1: 119-128

Zala, S.M., Potts, W.K., Penn, D.J. (2004) Scent-marking displays providing honest

signals of health and infection. Behavioral Ecology. 15:338-344

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Appendix 1

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Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics,CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GISUser Community

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LegendSouth-Island-2015

Appendix 2

2015 South Island Loggerhead Nesting Data45

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Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics,CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GISUser Community

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LegendSouth-Island-2016

Appendix 2

2016 South Island Loggerhead Nesting Data46

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Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics,CNES/Airbus DS, USDA, USGS, AeroGRID, IGN, and the GISUser Community

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LegendSouth-Island-2017

Appendix 2

2017 South Island Loggerhead Nesting Data

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LegendX Treatment-Zones

South-Island-2018

Appendix 2

2018 South Island Loggerhead Nesting Data with Treatment Zones48

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LegendX Treatment-Zones

Depredations

Appendix 2

2018 South Island Coyote Depredation Data with Treatment Zones49

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LegendX Treatment-Zones

9-D-Nests

Appendix 2

2018 9-Day South Island Loggerhead Nesting Data with Treatment Zones50

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LegendX Treatment-Zones

9-D-Dep

Appendix 2

2018 9-Day South Island Coyote Depredation Data with Treatment Zones51